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keshikeshi
Japan
3 Posts |
 Posted - 10/02/2019 : 06:22:25 AM
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Origin Ver. and Service Release (OriginPro 2019b ):
Operating System: Windows 10
Hello,
I'm trying to fit the NMR experimental data
(Chemical shift (y) vs solution initial concentration (x0)
with the next function,
y=(1-x1/x0-s*K*x1^2/(x0(1-K*x1))
Here, x0 and x1 are variables, s and K are parameters.
And, x0=(1-s)x1+[s*x1/(1-K*x1)^2], that X1 is the roots of cubic equation.
I don't know how to add constraints between two variables in the global fitting.
Any comments are helpful and valuable.
Thanks in advance.
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YimingChen
1669 Posts |
Posted - 10/03/2019 : 09:23:45 AM
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Hi,
Do you have the data for x1? Or you just have the data of y and x0? Thank you.
James |
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keshikeshi
Japan
3 Posts |
Posted - 10/03/2019 : 4:26:14 PM
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Hi James,
Thanks for the comments.
I just just have the data of y and x0.
I'd like to guess X1 as a result of fitting. |
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YimingChen
1669 Posts |
Posted - 10/03/2019 : 5:15:11 PM
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The only way I can tell is to rewrite y=(1-x1/x0-s*K*x1^2/(x0(1-K*x1)) as a quadratic equation of x1, and solve x1 to be x1 = f(y, x0). Substitute x1 in x0=(1-s)x1+[s*x1/(1-K*x1)^2] with f(y,x0), then perform implicit fit on your y, x0 data with the resulting equation.
James |
Edited by - YimingChen on 10/03/2019 5:15:56 PM |
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keshikeshi
Japan
3 Posts |
Posted - 10/06/2019 : 4:39:10 PM
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Hi,
Actually, the equation is the cubic function of x1, which is making the situation difficult. Anyway, I will try implicit fit.
Thanks, in advance. |
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Fitting with constraints for two variables